Switcheroo
by NuclearNik
Summary: Neville agrees to help Hermione with something. For science, of course.
1. The Beginning

When Neville had agreed to participate in a "scientific experiment," he hadn't really thought it through. Smart, pretty, kind Hermione Granger had asked for his help, and who was he to deny her?

It really was hard to say no when she turned those big, bright eyes on you.

So he'd agreed, without really asking for further information. He'd thought maybe she would have some questions about plants, that she'd want to study and observe certain flora for Herbology or something.

That was not the case.

He met her behind greenhouse two. It was a Hogsmeade weekend and they pretty much had the grounds to themselves.

He'd been waiting no more than a minute when she came bustling up, arms full of notebooks and a small bag making a mysterious _clink _noise like glass jars being jostled.

"Hello, Neville! Thank you so much for helping me with this. I very much appreciate it. No one else could be bothered, you see, and I really wanted hands-on experience—books are wonderful but there's only so much you can learn from a page, after all, and with NEWTS coming up—"

She was speaking at a rapid-fire pace, and Neville was finding it rather hard to keep up with her as she neatly stacked the notebooks on the worktop before reaching into the bag with one hand and pulling out two small bottles, chattering all the while.

"—Anyway, these notebooks are for recording our findings. I've made columns with different categories: general observations, differences, similarities—"

On and on she went, explaining her plan. Finally, she was done, and she turned to him with an expectant look on her face.

"Any questions?"

"Well, er, what is it exactly that we're doing?"

Her brow furrowed just a bit. "Oh, didn't I tell you yesterday? I was sure I did."

She looked upset that she might have forgotten one step of whatever grand plan she had going on, so he rushed to reassure her that she probably had told him, but he was just forgetful.

She perked up at that, going into teacher mode and explaining their mission for the day.

"Polyjuice is rather limitless when it comes to intraspecies transformations. As you know, gender, age, and ethnicity can all be played with. Last week I wrote a quite in-depth essay about polyjuice for extra credit and during my research, I discovered there is very little information on what a person feels when changing from male to female, or young to old. I think it would be helpful to have that information available. In order to do that, someone needs to perform polyjuice switches in each of those categories. Professor McGonagall has agreed to help with the age difference portion. But I need someone to help me record findings for the gender switch. With so few eighth years returning, there wasn't anyone that wanted to help—though I don't know why. Being the first to record new data is a rather exciting prospect, don't you think?"

He nodded at her. He supposed he did understand what she was saying because he could admit that discovering new things about plants—both magical and mundane—gave him quite a rush.

"Yeah, okay. I'll help you."

"Great!" A beautiful smile lit up her features, and then she was turning back to the countertop to grab the notebooks, holding one out to him expectantly.

"Before we drink the potion, we need to record baseline data first. Here, write down as much as you can about what you currently see, feel, hear. Try to explain how your body feels, the height it stands at, the weight of your limbs. That will help us to clearly see the differences between the beginning and ending data.

"Right, okay." Taking the notebook from Hermione's outstretched hand, Neville set to writing how he currently felt in his body.

They stood side-by-side at the worktop with elbows occasionally bumping as they wrote, the _scritch scritch _of quills against parchment sounding loud in the silence.

When Hermione was done with her notes, she set the quill on the counter and waited patiently for him to finish.

Having done the best he could, Neville finished up and took the bottle from her hand, uncorking it. He plucked a strand of hair from his head and dropped it in, watching as Hermione did the same. His potion turned light green, a bit like the tentacles of a flitterbloom plant. He gave it a sniff. It didn't smell all that bad, something he was grateful for because it would be rather embarrassing if Hermione had to drink what was essentially the essence of himself and it turned out he stank like stinksap.

"Ready?" he asked, waiting for the go-ahead from Hermione.

She nodded, switching bottles with him before clinking her glass to his in a cheeky toast and tipping it to her lips.

She looked so pretty like that, elegant neck curving back, pink lips pursed around the glass.

_Get ahold of yourself, mate. This is about science._


	2. The Switch

Shaking his head to rid himself of his distinctly unacademic thoughts regarding Hermione, Neville glanced at the little bottle before gulping down the potion. It was a pale lilac colour, almost iridescent.

He wasn't sure what he'd been expecting, but it tasted good, like lemonade and strawberries.

It was no surprise Hermione's particular strain of polyjuice was sweet and nice to look at.

As the potion kicked in, Neville's skin started to tingle. Pain shot through him and he hunched over himself, closing his eyes and waiting for the sickening sensation to stop. He was hot—swelteringly hot like he was on fire—and his bones shifted, popping and aching as they shrunk.

When he opened his eyes once more, he was suddenly seeing the world from a very different view. When he looked at Hermione, he realized his head barely came to her, er, _his _chest. He'd never really thought of himself as a tall person, but looking up at himself now he felt like he was a giant compared to Hermione's petite size.

He'd never really thought of her as small. She was one of those people whose personalities were so larger-than-life that it made them seem to have a bigger presence.

"It worked! Perfect!" Neville heard his own voice say, pitched a bit higher than he would normally speak as Hermione got used to being in his body.

She handed him a notebook. "Here's what you wrote before. Look at that and then record the differences."

The very first difference was his centre of gravity. It was different in Hermione's body, and it threw him off balance.

He wrote that down.

Next was the missing parts and extra, umm, areas on his body. He thought that was pretty self-explanatory but Hermione peered over his shoulder and asked him to please elaborate "For the sake of science, Neville."

So he did, with a blush he could feel climbing up his unusually slim neck.

And so it went, with Neville writing things down and Hermione either approving them as sufficient or asking him to include more information.

When they had recorded enough to please Hermione, she announced that it was time to move on to stage two, but that they first needed to change clothes. She went behind a massive flowering bush in the corner of the greenhouse and floated her clothes to him.

With a quick look around to make sure no one was about, Neville stripped out of the now too-big clothes and put on what Hermione had given him. The tiny socks to cover her tiny feet were still warm from her body as Neville pulled them on and slipped his feet into the sensible Mary Janes.

When he heard a rustle from the direction of the bush, he looked up to see himself—not himself, _Hermione—_emerge from behind it dressed in the clothes Neville himself had just been wearing.

By this point, it had been about thirty minutes and they had only half an hour more to record data.

With no time to waste, Hermione quickly explained that stage two meant they had to do things that they would typically do in their normal bodies in order to record the differences.

This next section, Hermione explained, would be about movement.

She turned into a drill sergeant, making them run laps and do sets of star jumps, then having them immediately write down their observations.

Everything felt different. When he jogged, certain areas bounced up and down. It was not pleasant. Neville wondered if there was a spell that could hold them in place and keep them from jiggling so violently or if girls just dealt with it. Hermione was slight, and her breasts were fitting for her frame. He imagined things could probably get very uncomfortable indeed if one were a bit more _well endowed _in the chest area. You'd need to strap those puppies down, he reckoned.

When they'd finished the exercises, they went back to the notebooks and wrote down every sensation they had experienced in their switched bodies.

Neville was starting to really hate this part—the part where he had to write down intimate details about another person's body. It was just _odd._

It wasn't that Neville was a complete prude, though. He'd had a good snog or three and a bit of heavy petting over the years, but going so long with so little confidence had held him back in the romance department. He was still figuring out what girls liked, what _he _liked.

When puberty had hit, and he'd grown a bit with a filled-out chest and limbs that were no longer limp spaghetti noodles, he'd felt so _off._ Like he was no longer at home in his own body. It had taken time to adjust, and if he were being honest, he wasn't sure that he _had _fully adjusted yet.

He was still learning how to be the Neville that knows his strengths, knows what he wants and how to achieve it.

His work-experience with Professor Sprout had certainly helped. He got to shadow her and be her teaching assistant, and he soaked up all the knowledge he could. He wanted to be where she was, someday. A life devoted to plants and teaching. Perhaps he would even apply at Hogwarts. Who knew what the future held?

Realising he'd gotten caught up in his mental reverie, Neville went back to writing in the notebook, trying his level best to be as scientific and precise as possible.

_*Uncomfortable up and down movement in the chest region _

_*Different centre of gravity calling for an adjustment in stride whilst running_

This time, he'd gotten past the awkwardness and was able to take notes without so much a blush. He wrote down a few more things and was rather proud of himself when Hermione found his notes to be sufficient and didn't even ask him to elaborate on anything.

Their time in one another's bodies was quickly coming to an end, and Neville found that he was just the teensiest bit disappointed to go back to his boring, normal body and life.


	3. The Kiss

Hermione was leaning over the workable, flipping pages in the notebooks and checking to see if they had enough data.

Neville waited patiently, using his wand to give some water to a Bubotuber plant that looked a bit parched and trimming some excess leaves off of a trailing nasturtium.

"All done," he heard his own voice say quietly, and he turned around to see that Hermione had closed the notebooks and packed up the supplies she had brought.

"There is one more thing," she said with a slightly unnerving glint in her eyes.

She walked up to him with her shoulders squared as if she were psyching herself up for something.

She was close enough that Neville had to look up to meet her eyes, and he saw freckles on his own face that he'd never really noticed before.

Fiddling with her hands, Hermione finally lowered her gaze and looked him in the eyes. "I was hoping we could, well, kiss in our switched bodies before we change back. This is just for my own personal research, of course. But I find that I'm insatiably curious to know what it feels like to kiss someone when you're not in your own body. We can only ever feel our own personal sensations, and this is an opportunity I don't want to miss. But if you're uncomfortable, that's quite alright. Please don't feel pressured. I just thought—"

"Let's do it," Neville said with far more confidence than he actually felt. "Might as well give it a go, while we can. For science."

She nodded briskly but Neville saw her throat bob with a rough swallow. "Yes. Science."

Now, that was interesting. It appeared he wasn't the only one with nerves in this moment. Did that mean she had a crush on him too? She certainly seemed rather flustered at the prospect of kissing him, but that could be chalked up to the fact that they were in each other's bodies and this whole thing had been a bit awkward. Either way, that was good, right? He could work with that.

Neville watched as his own hands controlled by someone else reached for his, well, _her _face, brushing a few wild curls behind his ear.

_This is really happening. I'm about to kiss Hermione Granger, or uh, she's about to kiss me. We're about to kiss each other? Crickey, stop thinking, Neville!_

Hermione in Neville's body was rather suave, moving with ease and a little bit of swagger. She reached for his chin, tucking her fingers beneath it and tilting his head back.

When their lips met, Neville was surprised to find that his were softer than he thought. It felt good kissing her like this, and Neville decided that the novel feeling of being the one to be pursued was rather intriguing.

When he felt a tongue tracing the seam of his lips, he pulled back. A kiss was fine, but a full-on snog session in the wrong bodies was just a little too strange for him.

"Hermione, I—"

"I'm sorry, did I do something—"

They spoke at the same time, and Neville motioned for Hermione to continue.

"Did I do something wrong?" She looked at him with a wrinkle between her brows, worry in her eyes like she thought she must have crossed a line.

"No!" Neville cleared his throat. "I mean, no, you didn't. Everything is fine. I just… If I'm going to be snogging someone, I'd rather it be the pretty girl I have a crush on—not myself."

Her eyes widened, but at that very moment the potion started to wear off, their skin bubbling and bones shifting.

When the haze of pain from the transition lifted, Neville opened his eyes to see that he was once again looking down at the little witch before him, back in her own body.

Now that he was back to himself again, he decided to try his luck.

"Neville—"

"Would you maybe want to—"

When they both opened their mouths at the same time, _again_, Hermione stopped and smiled at him, encouraging him to go on.

He looked everywhere but her, nervous now. "I thought maybe we could, you know, try it again?"

"You want to kiss me?" she asked with a lopsided smile and a sparkle in her eye.

Gathering his courage, Neville met her eyes and said, "Yes. I do."

"Well that's convenient," she said, her smile growing even bigger, "because I find I want to kiss you as well. But perhaps we should get back into our own clothes," she said, gesturing to the too-tight top and ridiculous skirt Neville was currently sporting.

This time they simply turned their backs on each other and threw the clothes over their shoulders. Neville had just buttoned the fly of his trousers when suddenly his arms were full of warm witch and bushy curls. She had launched herself at him, and he was thankful he'd had the wherewithal to catch her as she tightened her legs around his hips and draped her arms over his shoulders to play with the hair at the nape of his neck.

She looked at him with those big, beautiful eyes, now only inches away from his own. "Hi," she said.

He pressed his forehead to hers. "Hi," he said on a sigh.

He shifted to place a kiss on her pulse point, just below her ear. He breathed in the fragrance of her skin, so heady and sweet.

Trailing kisses along the delicate column of her throat, Neville shifted her so she sat a bit higher on his hips, allowing him to reach the expanse of skin just below her collarbone, revealed by the open collar of her button-down shirt.

Though he didn't have all that much experience, you can't room with someone like "Lady-killer Finnigan" for seven years and not pick up a few tips.

Neville was good at watching. It's how he'd survived years of people thinking he was stupid and weak. You observe, and you adjust, and you go on.

As he explored Hermione, he followed her lead. When she melted into him at a certain touch, he paid special attention to that area. He followed her sighs and the sweet little moans that went straight to his dick.

Hermione lifted her head from his neck where she had been leaving little love bites and pulled back a bit, just enough to cup his face.

"Put me down a minute," she whispered, and Neville thought that was it. Game over. He wasn't sure what he'd done wrong, but the thought of upsetting Hermione in any way made his stomach turn.

He loosened the arm he'd wrapped around her back and helped her to slide down his body and get back on her feet. He felt his face grow hot as he turned around to give her space. "Sorry, I—"

"Come here." The voice behind him had a breathy quality to it, like perhaps she was as affected by their kissing and touching as he had been.

When he turned back around, she was slipping her wand back into her pocket. "I wanted us to have a little privacy." She was slowly undoing the buttons on her blouse, looking at him with flushed cheeks and dark eyes.


	4. The Moves

Going on instinct, Neville moved behind Hermione as she worked at the line of buttons on her shirt. Using one hand, he pushed her hair to the side of her neck, leaving the soft slope of her shoulder exposed. With his mouth on her neck, he brought his hands to her hips and pulled her back against him.

He felt her breath catch when her backside met his front. He pressed a kiss just behind her ear, his height providing him with the perfect view over her shoulder of the newly exposed smooth skin and peachy nipples.

He stepped back, just a bit, to slide the shirt off her shoulders and onto the floor. She turned around to face him, running her hands up under his jumper.

His confidence finally faltered when he felt her fingers touch his skin. She was so fucking pretty, and he was average. He kept active but still, he couldn't resist the occasional pumpkin pastie. If he took his shirt off, would she be disappointed in what she saw?

Hermione pushed at the hem of his jumper, so he closed his eyes and tugged it off. She'd been separated from him for merely a moment before she pressed herself back up against him, skin to skin.

Her sweet mouth trailed up his torso, leaving kisses at each rib before looking up at him and darting her tongue out to tease his nipple.

A jolt went through him when she did it again, a little firmer this time. _Fuck, that feels good._

When her hands went to the placket of his trousers, he stopped her. He lifted her to sit on the work table—just the right height for what he wanted to do to her.

"My turn," he said, running his hands up her sides to cup her breasts. If her mouth on his nipples felt good, surely it was the same for her. She was so responsive, reacting to his every touch, and he wanted to find out if she was that sensitive everywhere.

He kissed her first, deep and slow, sweeping his tongue into her mouth while he used his thumbs to rub back and forth over each of her nipples, kneading the soft flesh of her breasts with his hands.

When he pulled back, she chased his mouth and a thrill shot through him. She wanted him. This gorgeous creature wanted more of him. What a feeling that was.

He dipped his head to her chest, kissing each puckered tip before taking one into his mouth. He watched and listened for signs that she was enjoying it, learning what she liked and didn't like.

Her hands had made their way to his head, clutching at his hair.

He was so far out at sea, and he had no idea how to proceed. But he knew what he wanted.

He wanted to taste her.

After lavishing her perfect breasts with attention, he pulled back and gently pushed at her shoulders, encouraging her to lie back on the worktable. Summoning all the Gryffindor bravado that he could, he ran his hands up her thighs, starting at her knees and moving ever higher, pushing her skirt up as he went.

Her breathing was laboured, and Nevile watched Hermione's belly tremble when he brushed his fingers across her soft skin.

He wanted to be sure that she was entirely on board, so he tucked his index fingers in the waistband of her cute pink knickers and said, "May I?"

She nodded up at him, smiling like a siren.

Slowly—so slowly it was almost painful—he pulled the knickers down her legs, eyes fixed on what was revealed by their removal.

_Bloody Hell._

Gathering the knickers and tugging them off from around her feet, he set them carefully beside her on the worktop—they were so lovely and delicate he didn't want to ruin them. They had to be expensive, right? He really wasn't very knowledgeable on the subject of women's underwear.

Somewhere in his peripheral vision, he thought he saw one corner of Hermione's mouth quirk up in a smile at his careful treatment of her underthings, but he was too far gone to focus on anything but the beautiful girl spread out before him. Before he could say anything, she was unbuttoning her skirt and lifting her hips to wiggle it down her legs.

He grasped down blindly but wasn't fast enough, and the skirt fell to the dirty ground. He'd started to move to pick it up when Hermione said, "Neville, it's alright. Just leave it." He was about to protest that there was no reason to ruin a perfectly functional piece of clothing when she moved her hands up her own body to pluck and pinch at her nipples.

Neville lost all sense of time for a moment as he watched her touch herself, contented sighs floating from her. He was sure he'd never been more turned on than in this moment. Not even when he'd found a girly mag under Seamus' bed in fourth year and discovered what an erection was for.

She made a noise, a little louder than the last one, and it pulled him out of his daze to focus again on his task.

"You look—you are… fucking beautiful."

He didn't usually swear much, as his gran would tear a strip out of his hide if he ever did, but if there were ever a moment to use those dirty words, it was now.

He started at her belly button, dipping his tongue inside and then trailing his mouth from one hip bone to the other, hands coming to rest on her thighs when she started to fidget.

Bringing his thumbs to her centre, he opened her up, just a little, just enough to see the hint of slickness around her opening. He wanted to taste it, this proof that he had made her body hum. _Him_, it was him who had done that—dopey Neville Longbottom.

He brought his mouth to her centre, and suddenly he was feasting on her, repeating a movement when she keened or her back arched up off the table, changing tactics when she didn't.

It felt so good to do this, to make her feel good.

He could get used to this.

Tentatively bringing a finger to her opening, he pressed in gently and waited for her reaction.

When she reached down to bring his hand closer to her and said, "More," Neville pushed one finger inside her, slowly pumping in and out. When her hips began to move in time with his fingers, he added another, stretching her just a bit.

Fucking hell, she was so soft, and warm, and _tight._ He couldn't have imagined that Hermione would feel this good.

He pulled back just a bit to look at her, and he realized he'd been neglecting the little hooded nub above her centre. He couldn't remember what it was called, but he knew it was essential to know where it was. He'd heard Lavender moaning to one of her friends about how woefully inept guys were at finding and engaging that spot.

So, with that in mind, Neville rubbed his thumb across it, back and forth a couple of times. Hermione's thighs tensed at the touch. He looked up quickly to make sure it was the good kind of tensing and was relieved when he heard her say, "_Yes, there."_ A small, breathy whimper came from her and spurred him on.

He tried to keep his fingers and tongue moving in tandem, alternating his movements from soft and slow to firmer and faster.

Her walls began to flutter around his fingers, and he could tell she was close.

He focused all of his attention on that little nub again, and that seemed to do the trick.

Hermione cried out as he pushed her over the edge. He tried to prolong her pleasure as much as he could before gentling his movements, pulling back a bit to press kisses to the inside of her thighs.

When Neville stood to his full height, he looked down at Hermione where she lay on the worktable as her eyes blinked back open, a sated look there now. He thought to himself that perhaps he'd never seen anything prettier.


	5. The End

Hermione hopped off the table, smiling and saying, "My turn." She made to drop to her knees in the dirt, and Neville knew what was coming. He was both exhilarated and nervous as hell as he put out a hand to stop her.

"Wait, just a second." He bent down and snatched his jumper from where it had been lying, and smoothed it over the ground to give her something to kneel on. The greenhouse was all dirt floors and loose pebbles.

She seemed a little taken aback by his gesture, but she just grinned up at him and whispered, "Thanks."

Her hands reached up to undo his trousers, but she had trouble with the last button. "It's snagged. Can you—?" She gestured in the general direction of his crotch. He fiddled with the button, finally getting it loose so she could tug the fly open.

She brushed her hand over the top of his boxers, where he was already half-hard. When she cupped her hand and pressed a little stronger, he nearly whined.

_Bloody hell that feels good._

She teased him through the fabric for a bit before slipping her fingers into the waistband of his boxers, pulling them down just enough to free his cock.

When Hermione wrapped her fingers around the base, Neville thought he might stop breathing. She pumped him a few times before sticking out her tongue to give the head a tentative lick.

_Oh wow._

Right as he moved to brush the stray hair back from her face, she closed her mouth around him and sucked.

He saw stars. Before he could stop it, his fingers tangled in Hermione's curls and he pulled her head forward.

When Neville realized what he'd done, he immediately let go, stammering an apology for being rough with her. She reached up with her unoccupied hand and snagged his wrist. Bringing his hand back to her hair, she pulled away from him to say, "It's alright. I'll tell you if I don't like something, okay? Just let yourself feel, for a minute." She smoothed her hands down his thighs as if to calm him, and he realized he needed to chill out and follow her lead.

The look she gave him as her mouth once more engulfed the tip of his cock was downright sinful. Naughty was a good look on her.

The edges of his vision went a little fuzzy, and then he was lost to sensation. Everything Hermione was doing felt good, _too good_, and he couldn't believe that this was where his typical boring Saturday had ended up.

He felt a tingle start at the base of his spine, and as Hermione did some clever manoeuvring with her hand and mouth moving in tandem, he knew he was right on the edge.

He wasn't really sure what to do, but he figured it probably wasn't polite to come in someone's mouth without discussing it first. With the hand in her hair, he tried to move her off of him, but she wouldn't relinquish her hold, shaking her head a little and looking up at him.

There was no way he could hold off any longer, so he stopped trying to tug her away and just let himself go, hoping he had understood her correctly.

When he reached his peak, it felt like it went on forever. When he was finally spent, Hermione pulled back and gently pressed her lips to the tip of his now-sensitive cock, smiling mischievously before licking up stray drops like he was an ice lolly.

When their breathing had slowed back down to a reasonable pace, and they were clothed once again, Neville was overcome with shyness. Despite what they'd just done together, he felt a bit awkward and bumbling, and he wasn't sure what to say now that it was over.

He needn't have worried. Of course, Hermione took charge.

After pulling her hair—even more tangled than it was before—into a ponytail with a stretchy looking band, Hermione raised up on her toes and kissed him square on the mouth. Tasting what he assumed was himself on her lips was a strange sensation, though not altogether unpleasant. When she pulled back, pecking his chin one last time, she said, "That was great. Thank you. For doing that with me. You're an excellent kisser."

Neville felt a blush burn across his face at the compliment. Smiling down at his shoes, he scrubbed a hand over the back of his neck and said, "You really think so?"

"Well, obviously or I wouldn't have said it." When he lifted his head to look at her, he saw the corner of her mouth kicked up in a little smirk.

"Hermione, I— well, that was… It was—" _What could he say that wouldn't make him sound like an idiot? Amazing, incredible, life-changing?_ "—really great."

She looked pleased with herself as she grabbed the notebooks and her bag, fidgeting a bit and scuffing the toe of her Mary Janes across the dirt.

"I better go. I need to compile all of our findings from the experiment. Thanks again, Neville, really. So, uh, see you around?" There was a question in her voice, and Neville could only hope that meant she wanted to repeat today's actions at some point in the future.

Unable to speak more than single-word sentences, he nodded and waved, watching as she walked away.

As he went back up to his dorm, he thought about the events of the day and the strange and exciting turn they had taken.

Neville decided then that he _did_ quite like science, after all.

* * *

A/N: And we're done! Thanks for reading this self-indulgent silliness. I'm now obsessed with Neville and have started plotting a multi-chapter Neville/Hermione adventure, so that'll happen at some point. As always, I'd love to know your thoughts! Constructive criticism welcome.


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